Incandescent electric lamps



March 5, 1957 F. WOODWARD ETAL 2,784,338

INCANDESCENT ELECTRIC LAMPS Filed Aug. 22, 1955 8 ....nm'W-WMNMH# \0 l 8 @QUEUE/8 l 0% G,

United States Patent INCANDESCENT ELECTRIC LAlVIPS Frank Woodward and Hugh Helm, Preston, England, assignors to Siemens Electric Lamps and Supplies Limited, London, England, a British company Application August 22, 1955, Serial No. 529,655

Claims priority, application Great Britain July 8, 1955 Claims. (Cl. 313-273) This invention relates to electric incandescent lamps and more paritcularly to lamps for projection in which a number of filaments are connected in parallel.

For some purposes rapid incandescent and nigrescence is required and the desired high wattage is obtained by the use of a number of relatively low wattage filaments connected in parallel. This requires the use of fine wire filaments to assist the rapid cooling after the lamp has been switched off.

As it may be required to use a projection lamp in a situation in which it is liable to be subjected to shock or considerable vibration, it is necessary to take precautions against damage to fine wire filaments from this cause. lt is also desirable to guard against complete failure should one filament fail. When a number of fine wire filaments are connected in a parallel formation there -is a danger not only of contact with an adjacent filament by a failed filament but of arcing between the failed filament and an adjacent sound filament.

In the present invention a projection lamp is provided with a number of filaments connected in parallel and disposed circumferentially in superimposed parallel horizontal planes. The filaments are arranged in two sets and are supported by massive support rods, which may also serve as conductors to the filaments, secured in the lamp, conveniently in a pinch. The filaments of each set are in the form of semicircles and are terminated on separate support rods, there being a pair of rods for each set of filaments. The support rods for like ends of the filaments of each set may spring from `the same point in the pinch or they may be formed as two parallel branches from a single sealed stem. To guard against damage of the filaments by excessive vibration it is arranged that the filaments are supported along their lengths at equipctential points and these supports are anchored at each end to rigid members. The rigid members may be secured in insulating bridge pieces between the support rods at opposite ends of the filaments the arrangement providing improved rigidity and ensuring that the system vibrates as a whole.

For a clearer understanding of the -invention an exemplary embodiment will now be described with reference to the accompanying drawing in which a perspective view of a projection lamp according to the invention is shown. For the sake of clarity only one set of filaments and intermediate supporting means are shown in the drawing and it should be understood that the two sets of filaments are similarly disposed and supported.

ln the drawing, a lamp required to operate for example at 200 volts and rated at 2.8 kw. comprises a gas filled spherical bulb l having a capped neck 2 in which there is a pinch 3 in which are secured two nickel rods 4 and 5 which are electrically connected to contact points in the cap by wires sealed into the pinch 3 in known manner. Each of the rods 4 and 5 extends from the pinch 3 parallel with the axis of the bulb 1 and is bent outwards oppositely and again parallel with the axis of the bulb and after extending for a short distance is welded to a ICC pair of molybdenum rods forming pronged extensions of the rods, the prongs 4a and 4b forming extensions of rod 4 and prongs 5a and 5b forming extensions of rod S, the rods 4 and 5 and their extensions 4a, 4b and 5a, 5b forming support rods for the filaments. Assuming that the bulb is disposed with its axis Vertical, the filaments 9 are arranged in a vertical plane as horizontally disposed semicircles with their ends welded to one prong of each support rod. In the present embodiment fourteen 200 watt nlaments are supported in two similar sets of seven, the filaments of the two sets being co-planar and spaced vertically at a distance of 6 mm. and the ends of the filaments of the two sets being welded to prongs 4a, 5a and 4b, 5b respectively. Each filament consists of a semicircle of wire of tungsten or tungsten in which a small percentage of alkali metal silicate is incorporated or a ltightly woundhelix of such wire, the plan view of the whole assembly of filaments being a circle of, for example, 48 mm. diameter with two diametrically opposite gaps formed by the spacing between the prongs of each support. Two ceram-ic bridge pieces 6 and '7 extend from between prongs 4a, 4b to between prongs Sn, 5b at points above and below the filaments 9 respectively and are held in position between the prongs by nickel strips 8 welded to the prongs of each support immediately above and below the bridge pieces and by molybdenum wires 3a two of which pass through holes in each bridge piece at each end thereof and are bent oppositely so as to iie against the strips 8 to which they are welded. ecured in the bridge pieces 6 and 7 by bending round it and passing through suitably disposed holes in it are a number of rods 10, of for example, molybdenum, projecting from each side, there being four sets of, for example, six rods in each set and two sets for each bridge piece the lengths of corresponding rods of each set being equal and such that their ends lie along a circular path of the same diameter as that of the semicircularly disposed filaments 9. Between the ends of correspondingly positioned rods 10 in each of the two bridge pieces 6 .and '.7 and welded thereto are taut molybdenum wires lili over each of which and before it is secured to the rods it? is passed a helix of molybenum wire 12, the helix l2 vbeing interrupted at distances corresponding to the position to be occupied by the filaments 9 and there formed into loops i3 inV the form of turns of large pitch and diameter to support the filaments 9 which pass through the loops so formed. The helices 12 are spot welded at their ends to the molybdenum wires 11. The bulb 1 may be provided with a mirror surface as required.

What is claimed is:

1. An electric incandescent lamp comprising a trans lucent sealed bulb, a plurality of filaments disposed within the bulb n co-planar sets as semicircles with their centres lying on a common axis, support rods one pair for each set of filaments to which the ends of the filaments are connected, intermediate support wires anchored at each end and disposed at right angles to the planes of the filaments so that each support wire intersects the filaments of a set at equipotent-ial points and means for supporting the filaments at each of said intersections.

2. An electric incandescent lamp according to claim l including a base for said bulb sealed thereto, the support rods being forked and the common part of each fork being secured to said base, refractory insulating members secured between the forked parts ot' each support rod beyond the planes of the filaments providing means for the anchoring of said intermediate support wires.

3. An electric incandescent lamp according to claim 1 including a helix of wire surrounding closely each intermediate support wire the ends of each helix being welded to the surrounding support wires, a loop being formed 4. An electric incandescent lamp according to claim 2 including rods of different lengths secured in and projecting from each of said refractory insulatingnmembers on each side thereof the ends of said; rods lying along the circumference of a: circle of' radius equal to that of the laments, the intermediate support' wires; for oneset of filaments being secured to the free ends-of' said rods projectingfrom the corresponding side ofjy the refractory insulating members and the intermediate support wires for the other set of filaments being secured to the free ends of the rods projecting from. the' other side of Said refractory members.

5 An electric incandescentmulti-lament lamp comprising a translucent sealed bulb capped; at one end', a pinch sealed to said capped end, forked support rods secured in said pinch and spaced. equidistantlyfrom the bulb axis and extending in planes parallel to said axis, a plurality `ofseniicircular filaments disposedI within the bulb in parallel planes in two sets one on eachside of and at right angles to the bulb axis the centres of the filaments lying( along thel said* axisandM the ends of thelaments being connected to one fork of each of the forked support reds, refractory insulating members held between the forked ends of the support rods for each end of the laments and lyingin planes beyond those of the filaments, rods secured in and projecting from the refractory insulation members on eachside thereof and at right angles thereto the ends of said projecting rods lying along the circumference of acircle of radius equal to that of the filaments, intermediate support wires disposed parallel to the bulb axis and welded to the free ends of rounding closely each intermediate supportwire the. ends of a helix being welded to the support wire, said' helix being formed with open: turns at thepoints of intersection of the surrounded support wire with a filament between which and the support wire the filament passes.

No references cited. 

